ML20084U753

Comments on Requesting Addl Info on Main Steam Safety Valves.Angle of Discharge,Stress Analysis,Dynamic Load Factor & Header Stress Discussed

ML20084U753
Person / Time
Site:	Palisades
Issue date:	11/08/1972
From:	Lofy R PARAMETER, INC.
To:	Reinmuth G US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084U727	List: ML20084U753 ML20084U940
References
NUDOCS 8306290219
Download: ML20084U753 (5)

Text

, Page 1 of 4 n

\.)

and Attachment -1 a ra m e ter, snh c.

r Consulting Encinocrs

• Design - Analysis - Development 13543 WATERTOWN PLANC ROAD, ELM GROYf, W4SCONSIN 33122 786-7583 November 8, 1972 Mr. G. W. Reinmuth, Chief Technical Assistance Branch United States Atomic Energy Commission Directorate of Regulatory Operations l Washington, D. C. 20545 Copy: L. L. Beratan l

Reference:

AEC Contract AT(11-1)-1658 Task A, Consulting Services

, PAR: 72-73 A Assignment No. DC-102

Subject:

Review of Consumers Power Company letter of October 31, 1972 replying to questions on Palisades main steam safety valves

Dear Mr. Reinmuth:

1 The following comments apply to the eight points in the subject letter which in turn correspond to the questions set forth in the Regulatory document entitled " Request for Additional Information - Consumers Power Co.,

Palisades Plant Docket No. 50-255 :

1 The information provided is not responsive to the question which asked for justification of the thrust angle assumed. We do not feel that the discharge elbow has a long enough radius to turn the steam 570 or even 450 Looking through the elbow into the throat of the valve, a line of sight with an area approximately 4CT of the elbow cross section exists at an angle of about 270 above the horizontal (equal to a deflection of 300 from the 570 line).

h$$

wo The 120 deviation allowed by the analysis does not So relate to a maximum angle of deficction that has been by demonstrated to result from valve discharge. Because Q(g the stress levels in both the elbow and header (See Attachment -1) are sensitive to the angic assumed in mo the analysis, it is of utmost importance to justify Y the maximum angle of deflection expected as a starting 8$ point. It appears that this has not been done, c)o.a.

The fact that an angle of only 120 is allowed within

- A rim a ,, 3,.c. O o  ?>ce -2 C O N S U LTI N G E N GI N E E R S ELM G R O V E, WISCONSIN Mr. G. W. Reinmuth -

USAEC-RO November 8, 1972 B31.1 stress limits indicates that the design is less conservative than originally thought by the licensee.

(This allowable angle was reported as 22.80 in the CP letter of September 15, and report verbally as 17.50 by the Bechtel representative in the September 27 meeting at Bethesda.) ,

2. Without reviewing the analysis, it is not possible to comment on the calculated maximum discharge force of 14,200 lbs. It seems reasonable in terms of data published by Crosby. The investigation should have looked into the effect of steam discharging at an angle flatter than the 57 and impinging on the separately supported dishcarge stack.

3. The basis for calculation of a dynamic load factor appears adequate. It is agreed that the com-binadstresses using the load factor can be compared with the material yield strength,which is comparable to 1.5Sa, This is a technical evaluation which goes beyond the applicable Code, B31.1.

4. As developed in our report, DC-102, September 25, 1972, the 1/2" reinforcing pad does not contribute significantly to header stiffness or reduction of Bijlaard stresses. We do not feel that it is correct to use the total thickness of 1.75" which includes pad in the stress calculation, except possibly for the pressure stress component. The results of analyses which we consider more accurate, but possibly somewhat conservative are presented in Attachment -1. We believe the licensee's calculation defines a lower bound for stress levels at the weld-o-let to header connection, rather than an " upper bound".

5. No Comment.

Page -3

' pa r a,m e!a r, c n c. o O C O N S U LTI N G E N GIN E E 2 5 ELM GROVE, Wl5 CON 5tN Mr. G. W. Reinmuth USAEC-RO November 8, 1972

6. A review of Attachment -A, indicates that the 1.3 dynamic load factor was apparently not applied in calculation of the longitudinal stresses reported for locations a_, b, and c. Our calculations show some-what higher stresses without the factor, the discrep-ancy being attributed to determination of the length of the moment arms in scaling the Be c htel layout drawing No. M-79, Rev. O.

We calculated stresses at location d, using the

" assumed 1.75" header wall" and have duplicated the stated results. In this case, it appears that the 1.3 dynamic load factor was applied. Stresses at location e, were not checked. Our previcus work in report DC-102, indicated that the stresses at the location e, were generally lower than at d,. The duplication of the licensee's reported 26,280 psig header stress at point d, does not indicate our concurrence. As indicated in Item -4 above, the value results from an assumption of an equivalent 1.75" wall thickness which is considered to be grossly non-conservative.

The answer to question (6) indicates that the Summary of Stresses assumes the " smallest justifiable" thrust angle. As indicated in (1) above, this angle is not considered to have been " justified".

7. Contained in this response is a statement that

"----the design conforms to Code within the degree of conservatism inherent in the assumptions made." It is two of these assumptions which give us a problem.

First is the assumption that "---the blowoff thrust would acc perpendicular to the face of the discharge surface." (or vary no mare than 120). The second is that the 1.75" combined thickness of the header wall

, and pad can be used in the Bijlaard calculation of stresses directly.

"""^

l l A,.:-cu,, L. O O C O N S U LTI N G E N GI Ni E R 5 ELM GROVE, WIS C O N 5 t N Mr. G. W. Reinmuth _

USAEC-RO November 8, 1972 The third paragraph under (7) presents the pot.sibility of applying the 3S m limit to safety valve discharge stresses treated as primary plus secondary stresses.

While the Code is not explicit on this, we do not believe that these stresses can be considered self-limiting and were satisfied to see that this rationale was not followed. We are in agreement with the limit of.1.SSm stated as being more appropriate in the fourth

, paragraph.

The'fifth paragraph under (7) indicates that a conser-vative margin is available in B31.1 stress levels to compensate for any deviation in the thrust angle. While no order of magnitudes are given, we do not believe that l credit can be taken for any conservatism in the Code.

For example, the non-conservative reported stress of 26,280 psi for the header at location d_ is beyond the 3 imits of 1.2Sh strictly allowd by R'11.1 and must be l compared with 1.SSm using methods which go beyond B31.1.

We do not understand the applicability of the last paragraph under (7) which talks of cyclic life. It would seem to imply that the system is good for 100,000 cycles. A specific fatigue evaluation applied to the highest stressed area would show a life orders of magnitude lower.

8. Stresses in the header, other than local at the safety valve connection, were not included in the scope of PARAMETER 's review on this assignment . We have no comments as to the contribution of valve reaction forces to general piping stresses.

If you have any questions or require any additional detail.

in this matter, please let me know.

Very truly yours, 4 , i TER, nc.

b M <

Richard A. Lofy Consulting Engineer Q

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